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Elements, Mixtures, and Compounds Help (page 2)

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— McGraw-Hill Professional
Updated on Aug 28, 2011

Examples

Example 1

Consider a rancher who has 100 horses: 24 are Appaloosas, 16 are Bays, 20 are Paints, and 40 are Palominos. What percent of Appaloosas does he have? He has 24 out of a hundred or 24%.

24/100 = n /100

n = 24%

Example 2

On a different scale, consider a typical classroom of 30 people. In this group, 3 are interested in English and journalism, 12 are interested in medicine and science, 6 are interested in teaching and education, and the final 9 want to pursue art, communications, and film. Since 30 is the total number of people in the class, we treat them as the whole or 100%. To figure out the percent of people who want to pursue various areas of further study, you divide by 30.

3/30 = 0.1 0.1 × 100 = 10%

(Multiplying by 100 allows you to figure out what percent of the whole is given.) 10% of the people in the class want to study English and journalism.

12/30 = 0.4 0.4 × 100 = 40% (science and math)

6/30 = 0.2 0.2 × 100 = 20% (teaching and education)

9/30 = 0.3 0.3 × 100 = 30% (art, communications, and film)

In chemistry, percent is used to record the amounts of an element within the entire material or form.

Let’s look at the human body. It is composed of many different compounds in various amounts. In science fiction terms, humans are referred to as “carbon-based units” since the average human is composed of 18% carbon by mass out of all the elements in the body. Figure 3.4 gives an idea of the variety of elements that combine to keep our bodies healthy.

Properties of Matter Percent

Fig. 3.4. A wide variety of elements are found in the body.

On a larger scale, the Earth is composed of many of the same elements found in our bodies as well as additional minerals and metals. Figure 3.5 lists the more plentiful elements in the Earth’s surface. The diversity of these elements supports and provides for millions of species of plants, animals, and minerals found on this planet. Without this large resource of diverse elements, or if it should swing far in the direction of one element over the others, our planet could become as barren as many others in our solar system.

One of the interesting things about our planet is the wide distribution of elements around the globe. Some of this diversity is due to the original formation of the continents and some is due to environmental factors, but the elements’ diverse properties play a huge role in making our world what it is today.

Without many different elements, life on Earth might still be just primordial ooze floating in pockets of sludge upon a primitive sea.

Properties of Matter Percent

Fig. 3.5. Elements of the Earth are varied, but many are very low in quantity.

Practice problems for these concepts can be found at - Properties of Matter Practice Test

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